Communications networks generally comprise two or more individual communication nodes, such as a computer or a phone, connected together by other network elements, such as a router or switch. These devices and network elements may be connected in a variety of ways, including via electrical and fiber-optic cables. A cable defines a connection, or communication link, between two adjacent network nodes, and a network path within a network is defined by a connection between two end nodes. Nodes located along the network path between the two end nodes are referred to as intermediate nodes.
One type of physical transport standard used to communicate between end nodes is Digital Signal 3 (DS3). DS3 (also known as T3) is a North American standard (ANSI T1.404) developed by the ANSI T1 subcommittee. A network link using DS3 has a total bandwidth of approximately 44.7 Mbps and is capable of multiplexing 672 potential channels for voice or data. A DS3 or physical T3 signal has the ability to carry characteristic information at the path layer.
Using DS3 cables that travel through intermediate nodes, network carriers establish dedicated network paths, interchangeably referred to herein as circuits, between two points, for example, between nodes in Boston and Chicago. Information regarding these network paths are often maintained in databases. Because the lines are dedicated, for efficient resource utilization and improved provisioning time, it is important for network carriers to be aware of which DS3 cables are being used in each of the network paths within its network. Accurate topological views of DS3 network paths are useful to efficiently utilize networking equipment, especially since network paths are constantly being added and altered in a network. Network carriers' DS3 circuit databases are difficult to maintain and typically contain a sizeable number of records that do not match the actual network paths in the network. These erroneous records cost the network carrier in both unused inventory and recovery labor as new circuits are being planned and implemented, and also when network paths are to be removed.
Prior approaches to updating these network path databases include manual tracing of paths and some automation to query network elements for their internal cross connects. Both of these approaches have limitations. Manual tracing of paths is very costly and time consuming. The retrieval of cross connect records by querying network elements can verify only a fraction of the path information and cannot produce end to end connectivity information. Payloads within packets have also been used for tracing purposes, but use of payload space within packets is dependent on either availability (i.e., unused payload space) or is intrusive and disrupts payload transfer.